[Anders Strandberg]

Anders Strandberg  asked the Naked Scientists:
   
Hi naked scientists,
 
A global warming question,
 
As we lose Arctic ice, and other ice as well, more sunlight will be absorbed and turned into heat instead of reflected. Arctic ice area is around 1 million km2 less at present compared to the 1980-2000 average. As open water absorbs around 70% more of the light my calculations get the following extra heat, assuming 100W/m2 reaches the surface at high latitudes, including cloud reflection.

100W/m2*0.7*365*12*60*60s*1E6*1E6m2=1.1E21  J/year
 
Anthropogenic global warming effect, around 1.6W/m2, this effect works on IR radiation from all surface area of the earth 24/7 as I understand it:

1.6W/m2*365*24*60*60s*500E6*1E6m2=2.5E22 J/year
 
Could not find a measure of the global dimming effect we still have from SO2 and particles but it certainly seems to be decreasing.

Is it possible to measure how the whole Earth's albedo changes and get a better idea of how much more sunlight we are now absorbing compared to before the industrial revolution, ice loss, forest loss, cities with asphalt etc?
 
What do you think of my calculations, a lot of assumptions as I have not found the data I really need. Interested in how natural feedbacks compare to the warming we have caused so far, seems ice loss and consequent albedo change a small part of total extra warming as of now but growing rapidly, when feedbacks start to dominate slowing the warming will be very difficult short of the new equilibrium.
 
regards,
anders

What do you think?

[RD]

Could not find a measure of the global dimming effect we still have from SO2 and particles but it certainly seems to be decreasing.

Is it possible to measure how the whole Earth's albedo changes and get a better idea of how much more sunlight we are now absorbing compared to before the industrial revolution, ice loss, forest loss, cities with asphalt etc?

Between the 1950s and the early 1990s the level of solar energy reaching the earth's surface had dropped 9% in Antarctica, 10% in the USA, by almost 30% in Russia. And by 16% in parts of the British Isles. This was a truly global phenomenon, and Gerry gave it a suitable name - Global Dimming. But again, the response from other scientists was one of sheer disbelief.

http://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_trans.shtml